Donepezil for dementia in Parkinson's disease: a randomised, double blind, placebo controlled, crossover study. - Ravina, B.; Puff, M.; Siderowf, A.; Farrar, J. T.; Gillespie, M.; Crawley, A.; Fernandez, H. H.; Trieschmann, M. M.; Reichwein, S.; Simuni, T. (Journal of Neurology, Neurosurgery & Psychiatry, 2005)